A supercharger installation is one of the most material modifications you can declare to a car insurer. It increases power output significantly, changes the car’s risk profile, and affects agreed value. Failing to disclose a supercharger or underdeclaring the associated power increase is a common — and costly — mistake. In a 2023 sample of rejected modified car claims, 18% involved undisclosed forced induction systems.

Why Insurers Care About Superchargers

Insurers assess risk primarily on the probability and cost of a claim. A supercharged car carries higher risk because:

• Higher power output increases accident probability and severity
• Higher performance attracts younger or less experienced drivers (statistically)
• Supercharged cars are more theft-attractive than standard vehicles
• Associated cooling, fuelling, and drivetrain modifications increase total build value

What to Declare When Adding a Supercharger

When declaring a supercharger installation, provide:

• The brand and model of the supercharger kit (Roush, Whipple, Edelbrock, Kenne Bell, etc.)
• The approximate power increase (before/after dyno figures are ideal)
• Associated modifications: intercooler, fuel system upgrades, ECU tune, clutch, drivetrain
• Whether the car retains full road registration and passes emissions testing

How Much Does Supercharger Insurance Add to Premiums?

Adding a supercharger typically increases annual premiums by 25–65% above a comparable unmodified car. The exact impact depends on:

• The power increase (a mild Roots blower adding 75hp is treated very differently from a 4-rotor Whipple adding 400hp)
• The car type and market value
• The driver’s age and history
• Whether track use is being added simultaneously

Finding an Insurer for Your Blown Build

Standard comparison sites rarely return valid policies for supercharged cars. Use specialist brokers who understand forced induction builds. Confirm that the quote explicitly covers the supercharger and associated modifications — not just ‘performance modifications’ as a blanket term. Get the cover note in writing before assuming you’re insured.

Agreed Value for Supercharged Cars

A quality supercharger kit and installation can add £3,000–£15,000 to a car’s build value. Standard market value policies completely ignore this. Request an agreed value policy that explicitly includes the supercharger system and associated modifications in the covered value. Provide receipts, photos, and a dyno sheet to support the agreed figure.